1. Field of the Invention
This invention relates to color diffusion transfer photographic materials and, more particularly, to color diffusion transfer photographic materials to be developed with a primary aromatic amino color developing agent.
2. Description of the Prior Art
There are many patents and patent applications on photographic materials for the color diffusion transfer process by a primary aromatic amino color developing agent as will be described later and various dye image forming processes, dye image-providing materials, layer structures, formats, etc., for these color diffusion transfer photographic materials are well known. However, all of these conventional techniques are of the type that dye images are formed by the reaction of dye image-providing materials and the oxidized products of primary aromatic amino color developing agents. In such color diffusion transfer photographic materials, it is as a matter of course necessary for the dye image to be stable. That is, the dye images transferred to an image-receiving element in a color diffusion transfer process are very unstable when the processing composition remains spread thereover either when a photosensitive element is stripped from the image-receiving element or when the photo-sensitive element is not stripped from the image-receiving element and the dye images usually fade with the passage of time or formation of stain usually occurs in areas not bearing transferred dye images, the so-called "blank portions" of the image-receiving element.
Although not many reports have been made, several techniques for overcoming these drawbacks have been made.
For instance, Japanese Patent Application (OPI) No. 5424/73 (corresponding to U.S. Pat. 3,743,504) shows that the addition of an aldehyde-bisulfite addition product is effective for preventing the formation of stain in the blank portions of image-receiving elements. It is believed that the additive causes a reaction with excess unreacted primary aromatic amino color developing agent to form a colorless product, which results in reducing the formation of yellowish brown stain by the diffusion of the unreacted primary aromatic color developing agent into an image-receiving element. Also, Japanese Patent Application (OPI) No. 15134/72 (corresponding to U.S. Pat. No. 3,725,063) shows that the incorporation of an isocyanate-bisulfite addition product in a polymer binder is effective for preventing the formation of stain in the blank portions and in this case, it is also believed that the additive can prevent the formation of stain in the same manner as described above. Furthermore, Japanese Patent Application (OPI) No. 3836/73 (corresponding to U.S. Pat. No. 3,730,713) shows that the addition of a bis(vinylsulfonylalkyl) derivative or a polymer thereof is also effective for the prevention of stains and in this case it is said to markedly suppress the formation of stains by the same action as above.
The aldehyde-bisulfite addition product, the isocyanate-bisulfite addition product, the bis(vinylsulfonylalkyl) derivative (or the polymer thereof) are effective for preventing the formation of stains in the blank portions of image-receiving elements as stated above but these materials exhibit only a slight effect for the prevention of fading of color images.
Furthermore, the stabilization of color images is generally very important in photographic materials adapted for use in a color diffusion transfer process using a primary aromatic amino color developing agent. That is, in an ordinary color photographic process, the developer remaining on color photographic materials after developing the image-exposed color photographic materials (it is well known that such a developer adversely influences the stabilization of images formed) is removed therefrom by such processings as fixing, water washing, silver removal, etc. In other words, in an ordinary color photographic process, a "removal of spent developer" procedure, preferred for the stabilization of images, is performed. On the other hand, in a color diffusion transfer process, the processed photographic material retains therein the processing composition (i.e., a removal of the spent developer from the image-receiving element is not performed), the color images formed are quite unstable as can be easily understood.